The nature of the feedback regulation of ACTH release by cortisol will be tested in normal men. Women are being studied similarly in a collaborating GCRC. We will administer a potent inhibitor of adrenal steroidogenesis before and then with concomitant pulsatile or continuous intravenous delivery of cortisol over 24hrs. This will tell us if a pulsatile cortisol signal shuts off ACTH secretion more efficiently.